September 27, 2011

Plug-in vehicles with small battery packs are better for the environment

Carnegie Mellon University's Jeremy J. Michalek and co-authors report that plug-in vehicles with small battery packs and hybrid electric vehicles (HEVs) that don't plug in can reduce life cycle impacts from air emissions and enhance oil security at low or no additional cost over a lifetime. But plug-in vehicles with large battery packs are more costly and may have higher or lower emissions than HEVs depending on where and when they are plugged in.

"Because vehicles with larger battery packs are more expensive, fewer of them can be subsidized, and that can result in lower total benefits," said Michalek, who recently received a $400,000 grant from the National Science Foundation (NSF) to analyze how public policy could help determine the types of vehicles built in coming years and how consumers might respond to these vehicles.

"It's possible that in the future plug-in vehicles with large battery packs might offer the largest benefits at competitive costs if the right factors fall into place, including sufficiently low cost batteries, high gasoline prices, low emission electricity and long battery life," said study co-author Mikhail Chester, assistant professor of sustainable engineering at Arizona State University. "But such a future is not certain, and in the near term, HEVs and plug-in vehicles with small battery packs provide more emissions benefits and oil displacement benefits per dollar spent."

"With increasing energy and environmental constraints, transitioning from conventional gasoline vehicles to hybrid and plug-in vehicles offers an opportunity for improving energy independence and air quality while helping to address global warming," said study co-author Constantine Samaras, an engineer at the RAND Corporation.